The disclosure of Japanese Patent Application No. 2001-100938 filed on Mar. 30, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The present invention relates to a pump unit in which a unit case, which houses a fuel pump, is hung from an upper wall of a tank by a unit case supporting flange. Especially, the present invention relates to a pump unit equipped with a height adjusting part to install fuel tanks with different heights.
2. Description of Related Art
As for a fuel pump which supplies fuel to an engine, an in-tank fuel pump, which is installed in a fuel tank, is widely used these days. Furthermore, parts surrounding the tank are integrated to reduce vehicle cost, and so on. As a result, a filter element, which filters fuel discharged from a fuel pump, is combined with the fuel pump. And the filter element and the fuel pump form a pump unit. Then the pump unit is hung from an opening on an upper wall of the fuel tank.
FIG. 3 shows an example of installing the above-described pump unit in a fuel tank. A pump unit 30 according to FIG. 3 includes a unit case body 35, a pump 32 (described later), and a filter element 33. A unit case supporting flange 34 is connected with the unit case body 35 by means of weld, and so on. The connected two parts form a unit case 31. An engaging claw 37 of an engaging part 36, which extends downward from the unit case 35, is engaged with an engaging hole 41 of a pump holder 40 which supports the lower end of the pump 32. As a result, the pump holder 40 is supported by the unit case body 35. A flange part 38 of the unit case supporting flange 34 is hung and fixed on an upper wall 39 of the fuel tank. As a result, the unit case supporting flange 34 supports the entire pump unit 30.
A filter housing part 42 is located on the side of the unit case body 35. The filter element 33 is housed and fixed in the filter housing part 42. A pump connection 43 is provided in the proximity of the filter housing part 42 and fits into an outlet 45 of the pump 32 through a grommet 44. An opening 46 of the pump connection 43 is connected with an upper-end opening 47 of the filter element 33, which is housed in the filter housing part 42, through a connecting space 48. The connecting space 48 is located on the underside of the unit case supporting flange 34.
As described above, the lower end of the pump 32 is placed on the pump holder 40 which is supported by the unit case body 31. The outlet 45, which is located at the upper end of the pump 32, is connected with the pump connection 43 through the grommet 44 and incorporated into the pump unit 30. A suction filter 51 is attached to a suction hole 50 of the pump 32. The suction filter 51 extends along a bottom wall 52 of the fuel tank to suck in fuel in the lowermost part of the fuel tank.
A fuel supplying part 55 is provided at the unit case supporting flange 34. As described above, fuel in the tank is supplied through the suction filter 51, the pump 32, the opening 46, the connecting space 48, and the filter element 33 to an engine from the fuel supplying part 55 after flowing through a channel surrounding the pump 32 (not shown). In the pump unit 30 described above, a height of the entire pump unit 30 needs to correspond to a length from the bottom wall 52 of the fuel tank to the upper wall 39 due to the following two reasons. The first reason is that the pump unit 30 is hung from the upper wall 39 of the fuel tank. The second reason is that the suction hole 50 of the pump 32 needs to be located in the proximity of the bottom wall 52 of the fuel tank to suck in fuel in the fuel tank as much as possible. However, a length from a bottom wall to an upper wall of a fuel tank differs depending on the type of a vehicle. Therefore, a height adjusting means is needed to use the same tank as much as possible and correspond to as many fuel tanks as possible.
To correspond to fuel tanks with different heights, structures shown in FIGS. 4A and 4B, for example, may be adopted. According to the structure shown in FIG. 4A, a pump unit is substantially identical to the pump unit 30 shown in FIG. 3. In this case, the pump unit is manufactured to be installed in the shortest fuel tank in which the pump can be fitted. The shortest tank has a minimum height of H1. When the pump is applied to a taller tank with a height of H2, as shown in FIG. 4B, a joint pipe 55 with a length of L1 (xe2x88x92H2-H1) may be provided between the pump connection 43 and the outlet 45 of the pump 32 to correspond to the height H2.
The joint pipe 55 is connected to the pump connection 43 through the grommet 44 at a unit connection 56 located at the upper end. At a pump connection 57 located at the lower end, the joint pipe 55 is connected to the outlet 45 of the pump 32 through the grommet 58. Therefore, fuel from the outlet 45 can he discharged to the opening 46, located at the pump connection 43 of the unit case body 35, through the joint pipe 55.
According to the structure adopting the joint pipe 55, relative relation regarding positions of the pump 32 and the unit case body 35 deviates vertically. As a result, the pump 32 moves relatively downward and the pump holder 40, which supports the lower end of the pump 32, also moves downward. Therefore, a housing 59 needs to be provided between the pump holder 40 and the engaging part 36 located below the unit case body 35. Regarding the housing 59, the engaging hole 61, which is provided at a unit connection 60 located at the upper end, is engaged with the engaging claw 37 of the engaging part 36. An engaging hole 63, which is provided at a holder connection 62 located at the lower end, is engaged with the engaging hole 41 of the pump holder 40. As a result, the pump holder 40 is fixed on the unit case body 35 through the housing 59, and the housing 59 supports the lower end of the pump 32. Therefore, a length of the joint pipe 55 is set to L1 which is equal to that of the housing 56.
According to the structure adopting the joint pipe 55 for adjusting height, the joint pipe 55, the grommet 58, and further, the housing 59 are needed. Therefore, it is inevitable that manufacturing cost for each component and assembly man-hour will increase. As a result, the end product becomes expensive.
Also, it is conceivable that a length of each part can be adjusted, as shown in FIGS. 5A and 5B, for example, to correspond to fuel tanks with different heights. In other words, like FIG. 3 and FIG. 4A, FIG. 5A shows the pump unit 30 which is manufactured to be installed in the shortest fuel tank in which the pump can be fitted. FIG. 5B shows, for example, when a height of a tank is changed from H1 to H2. It is conceivable that a length of the unit case supporting flange 34 be lengthened by L1 to correspond to the changed height. Furthermore, as shown in FIG. 5C, for example, when a height of a tank is changed from H1 to H3, it is conceivable that a length of the unit case supporting flange 34 be lengthened by L1 like the example of 5B and a length of the upper part of the unit case body 35 be lengthened by L2. According to the example shown in FIG. 5C, the joint pipe 55 is adopted like the example of 4B and lengthened by L3 to correspond to a tank with a height of H3. The example in FIG. 5C includes all the above-mentioned height adjusting means.
As described above, when the unit case supporting flange 34 or the unit case body 35 needs to be lengthened to correspond to fuel tanks with different heights, a volume of the connecting space 48, which is located between the opening 46 connected to the outlet 45 of the pump and the upper-end opening 47 of the filter element 33, increases in proportion to the lengths L1 shown in FIG. 5B and L2 shown in FIG. 5C. When fuel flows into the connecting space 48 from the outlet 45, the flow of the fuel slows down and then stagnates. As a result, gaseous components of the fuel collect gradually and turn into bubbles. Furthermore, a large gaseous space, which is so-called air stagnation, is formed in the upper part of the connecting space 48.
When the above-mentioned air stagnation is generated, the air stagnation eventually generates resistance to fuel flow, which exerts a negative effect on discharge performance of the pump 32 and contributes to engine failure such as knocking. Furthermore, when a length of the unit case supporting flange 34 and that of the unit case body 35 need to be changed, it largely increases the manufacturing cost of the end product due to the unfavorable following two reasons.
The first reason is that a mold of a component with a complicated shape such as the unit case body 35 can be expensive. The second reason is that, as described above, different molds are needed depending on a length of a component.
Therefore, it is an object of the present invention to provide a pump unit with the following two features. The first feature is that the number of added components to correspond to fuel tanks with different heights is minimized. The second feature is height adjustment can be carried out without generating air stagnation in a fuel channel in a unit case.
According to a first aspect of the present invention, a pump unit is provided with a unit case body which houses the pump, a unit case supporting flange which supports the unit case body and hangs the pump unit from a fuel tank, and a wall which is provided at an intermediate part and has the following two functions.
The first function is to fix the intermediate part, which adjusts a height of the pump unit, between the unit case body and the unit case supporting flange. The second function is to cover a fuel channel having an open upper portion, provided above the unit case body.
According to the first aspect, height adjustment of the unit case body and the unit case supporting flange are not necessary. Therefore, height adjustment can be carried out with inexpensive means and no difficulties. And it is not necessary to use many components such as a joint pipe and a housing, and so on. Therefore, the number of components can be decreased. An end product can be less expensive since both assembly time and component management can be decreased.
Furthermore, the fuel channel, which is covered by the wall provided at the intermediate part, can be made sufficiently small so that generation of air stagnation in the fuel channel can be prevented.